1. Field of the Invention
The present invention relates to a machining center and, more particularly, to a spare tool changing system for changing spare tools held in a tool magazine.
2. Description of the Related Art
Generally, a horizontal machining center has a horizontal spindle and a tool magazine supported on a frame on a level above the spindle. A plurality of spare tools are stored in a horizontal position in the tool magazine. An ATC (automatic tool changer) replaces a tool held on the spindle with a desired one of the spare tools. Spare tools which are not necessary for the present machining or damaged spare tools are replaced with different tools, removed from the tool magazine and carried outside the machining center.
A spare tool changing system for changing spare tools stored in a tool magazine is disclosed in JP-A No. 151539/1998 or JP-A No. 290339/1997. This prior art spare tool changing system takes out a spare tool from a tool magazine by an actuator, carries the spare tool in a horizontal position horizontally, transfers the spare tool in a horizontal position to a lifting device, lowers the lifting device to carry the spare tool to a tool changing station, replaces the spare tool with a different spare tool, and reverses those steps to carry the different spare tool to and store the same in the tool magazine.
Since this prior art spare tool changing system transfers the spare tool from the actuator to the lifting device, the spare tool changing system needs a special transfer mechanism and takes a long time for changing spare tools. Since the spare tool is held in a horizontal position all the time while the same is being carried, it is possible that the taper part of the spare part, comes off the lifting device, making a tool changing operation at the tool changing station difficult.
Accordingly, it is an object of the present invention to provide a spare tool changing system for a machining center, having a simple mechanism and capable of quickly, surely and easily changing spare tools.
According to a first aspect of the present invention, a spare tool changing system for a machining center provided with a tool magazine storing a plurality of spare tools in a horizontal position and disposed on a frame, to change the spare tools stored on the tool magazine includes a tool changer capable of putting a spare tool on and taking out the same from the tool magazine in a horizontal position; and a guide rail extending between a tool transfer station near the tool magazine and a tool changing station near a lower part of the frame to guide the tool changer for movement between the tool transfer station and the tool changing station.
In the spare tool changing system, it is preferable that the guide rail has a horizontal section for guiding the tool changer with the spare tool held in a horizontal position before the tool changer reaches the tool transfer station, a vertical section for guiding the tool changer with the spare tool held in a vertical position before the tool changer reaches the tool changing station, and a curved section for changing the direction of the tool changer, extending between the horizontal section and the vertical section.
In the spare tool changing system, it is preferable that the horizontal section is extended straight in a substantially horizontal plane on the frame, and the vertical section is extended straight in a substantially vertical plane on the frame.
In the spare tool changing system, it is preferable that the tool changer includes a carriage that travels along the guide rail, and a tool holding device supported so as to be movable on the carriage and capable of holding a spare tool.
It is preferable that the spare tool changing system further includes a tool holding device moving mechanism disposed near the tool transfer station and capable of moving the tool holding device supported on the carriage in directions perpendicular to and in directions parallel to the axis of the spare tool held on the tool holding device.
It is preferable that the spare tool changing system further includes a tool holding device shifting mechanism disposed near the tool changing station and capable of shifting the tool holding device supported on the carriage from the carriage in a direction perpendicular to the guide rail.
It is preferable that the spare tool changing system further includes a coupling mechanism for coupling the tool holding device and the carriage together while the tool changer is traveling, and a tool holding device releasing mechanism for releasing the tool holding device from the carriage at the tool transfer station and at the tool changing station.
The spare tool changing system according to the present invention is capable of quickly changing the spare tools by a simple mechanism by moving the tool changer directly between the tool transfer station and the tool changing station and of surely and easily achieving a tool changing work by altering the position of the spare tool to a vertical position at a position in front of the tool changing station.